1. Field of the Invention
The present invention relates to a method for fabricating a ceramic substrate and, more particularly, to a method for forming a polyimide thin film on a large-scale, weighty ceramic substrate through a simple method.
2. Description of the Related Art
Recently, as electronic components continue to be reduced in size and smaller electronic components tend to be increasingly preferred, compact modules and substrates have been developed by making electronic components more precise, patterns finer, and films thinner. However, when a commonly used printed circuit board (PCB) is employed for a small electronic component, drawbacks are recognized in that the PCB needs to be reduced in size, a signal loss occurs in a radio frequency area, and reliability is degraded in conditions of high temperature and high moisture.
Thus, in order to overcome such shortcomings, a substrate using a ceramic is in use. When a main ingredient of a ceramic substrate is a ceramic composition including a large amount of glass available for low temperature cofiring, the substrate is classified as a low temperature cofired ceramic (LTCC) substrate.
The LTCC substrate can be fabricated according to various methods. The LTCC substrate fabrication methods may be classified into a shrinkage method and a non-shrinkage method depending on whether or not the substrate is shrunken when fired. The LTCC substrate is advantageous in that it has excellent thermal and electrical characteristics, has high structural degree of freedom, and can be easily converged (or amalgamated) and compounded with different techniques.
In forming a single or multiple polyimide surface layers on the LTCC substrate, a surface layer formation material is coated by using a spin-coating method. However, due to the trend of an increase in the size of a semiconductor wafer and a ceramic substrate, the spin-coating method is not suitable for forming a uniform film of a weighty, large-scale substrate through a high speed rotation.